Oxepinamide F biosynthesis involves enzymatic D-aminoacyl epimerization, 3H-oxepin formation, and hydroxylation induced double bond migration.

Oxepinamides are derivatives of anthranilyl-containing tripeptides and share an oxepin ring and a fused pyrimidinone moiety. To the best of our knowledge, no studies have been reported on the elucidation of an oxepinamide biosynthetic pathway and conversion of a quinazolinone to a pyrimidinone-fused 1H-oxepin framework by a cytochrome P450 enzyme in fungal natural product biosynthesis. Here we report the isolation of oxepinamide F from Aspergillus ustus and identification of its biosynthetic pathway by gene deletion, heterologous expression, feeding experiments, and enzyme assays. The nonribosomal peptide synthase (NRPS) OpaA assembles the quinazolinone core with D-Phe incorporation. The cytochrome P450 enzyme OpaB catalyzes alone the oxepin ring formation. The flavoenzyme OpaC installs subsequently one hydroxyl group at the oxepin ring, accompanied by double bond migration. The epimerase OpaE changes the D-Phe residue back to L-form, which is essential for the final methylation by OpaF.

Purification and characterization of two grandiuvarones from Desmos chinensis leaves and their antimicrobial activities.

A novel aromatic compound, grandiuvarone B (5-acetoxy-3-benzoyloxymethyl-5H-oxepin-4-one), along with a known compound grandiuvarone A (5-acetoxy-6-benzoyloxymethyl-5H-oxepin-4-one) were isolated from methanol extracts of Desmos chinensis leaves. Their structures were determined by various spectroscopic techniques including nuclear magnetic resonance (NMR), high-resolution electrospray ionisation mass spectrometry (HR-ESI-MS) and circular dichroism (CD). Grandiuvarone A and grandiuvarone B are isomers and the S configuration of grandiuvarone B was reported for the first time. We then determined their antifungal activity against Aspergillus flavus. Results revealed that grandiuvarone B exhibited better antifungal activity against A. flavus, with MIC values of 0.01 mg/mL compared to grandiuvarone A (MIC values of 0.02 mg/mL). In the presence of each active compound at 160 µg/g of aquafeed, A. flavus growth was completely inhibited. Grandiuvarone B also showed antibacterial activity against the plant pathogen Ralstonia solanacearum.

Diketopiperazine-Type Alkaloids from a Deep-Sea-Derived Aspergillus puniceus Fungus and Their Effects on Liver X Receptor α.

Eight new diketopiperazine-type alkaloids including four oxepin-containing diketopiperazine-type alkaloids, oxepinamides H-K (1-4), and four 4-quinazolinone alkaloids, puniceloids A-D (5-8), together with two known analogues (9 and 10), were isolated from the culture broth extracts of the deep-sea-derived fungus Aspergillus puniceus SCSIO z021. Their structures were elucidated by spectroscopic analyses, and their absolute configurations were determined by Marfey's method along with comparison of their specific rotations and ECD spectra. The absolute configurations of 4 and 5 were further confirmed by a single-crystal X-ray diffraction analysis. Compounds 1-8 showed significant transcriptional activation of liver X receptor α with EC50 values of 1.7-50 µM, and 7 and 8 were the most potent agonists.

Alstoscholactine and Alstolaxepine, Monoterpenoid Indole Alkaloids with γ-Lactone-Bridged Cycloheptane and Oxepane Moieties from Alstonia scholaris.

Two new monoterpenoid indole alkaloids, alstoscholactine (1) and alstolaxepine (2), were isolated from Alstonia scholaris. Compound 1 represents a rearranged stemmadenine alkaloid with an unprecedented C-6-C-19 connectivity, whereas compound 2 represents a 6,7- seco-angustilobine B-type alkaloid incorporating a rare γ-lactone-bridged oxepane ring system. Their structures and absolute configurations were determined by spectroscopic analyses. Compound 1 was successfully semisynthesized from 19 E-vallesamine. Compound 2 induced marked vasorelaxation in rat isolated aortic rings precontracted with phenylephrine.

New compounds from a hydrothermal vent crab-associated fungus Aspergillus versicolor XZ-4.

Three new quinazoline derivatives (1-3), one new oxepin-containing natural product (4) and four new cyclopenin derivatives (5-7 and 9) have been isolated from an EtOAc extract of the Taiwan Kueishantao hydrothermal vent crab-associated fungus Aspergillus versicolor XZ-4. Their planar structures were established by HRMS, 1D and 2D NMR spectroscopic data analyses. The absolute configurations for compounds 1 and 4 were determined by chiral phase HPLC analysis of their hydrolysis products. The absolute configurations of 2, 3 and 7 were defined mainly by comparison of the quantum chemical TDDFT calculated and the experimental ECD spectra, and the absolute configuration of 5 was deduced from comparison of the optical rotation values reported in the literature. The presence of two atropisomers of 5 was established by NOE analyses. The Ile & Val units in compounds 1-3 allowed the assignment of a new quinazoline skeleton and it's the first time the configuration of isoleucine in the quinazoline skeleton was defined. A series of 7-methoxy cyclopenin derivatives were reported for the first time in this study. The bioevaluation of compounds 5, 7, 8 and 9 revealed inhibitory activities against E. coli at MIC values around 32 µg mL-1.

NMR reassignment of stictic acid isolated from a Sumatran lichen Stereocaulon montagneanum (Stereocaulaceae) with superoxide anion scavenging activities.

The phytochemical study of Stereocaulon montagneanum harvested in Sumatra (Indonesia) led to the isolation of 11 known compounds including two metabolites not previously described in the genus Stereocaulon, peristictic acid (8) and menegazziaic acid (10). The complete 1H and 13C NMR spectral assignments of stictic acid derivatives are reported with some revisions. Five depsidones belonging to the stictic acid chemosyndrome were superoxide anion scavengers as potent as ascorbic acid and with no toxicity on two human cell lines.

Three Pairs of New Isopentenyl Dibenzo[b,e]oxepinone Enantiomers from Talaromyces flavus, a Wetland Soil-Derived Fungus.

Three pairs of new isopentenyl dibenzo[b,e]oxepinone enantiomers, (+)-(5S)-arugosin K (1a), (-)-(5R)-arugosin K (1b), (+)-(5S)-arugosin L (2a), (-)-(5R)-arugosin L (2b), (+)-(5S)-arugosin M (3a), (-)-(5R)-arugosin M (3b), and a new isopentenyl dibenzo[b,e]oxepinone, arugosin N (4), were isolated from a wetland soil-derived fungus Talaromyces flavus, along with two known biosynthetically-related compounds 5 and 6. Among them, arugosin N (4) and 1,6,10-trihydroxy-8-methyl-2-(3-methyl-2-butenyl)-dibenz[b,e]oxepin-11(6H)-one (CAS: 160585-91-1, 5) were obtained as the tautomeric mixtures. The structures of isolated compounds were determined by detailed spectroscopic analysis. In addition, the absolute configurations of these three pairs of new enantiomers were determined by quantum chemical ECD calculations.

Two new phenolic compounds from the tuber of Sparganium stoloniferum.

Two new phenolic compounds, 2-(2-hydroxyphenyl)-4-methoxycarbonyl-5-hydroxybenzofuran (1) and 1-methoxycarbonyl-2, 3-dihydroxydibenzo[b, f]oxepine (2), were isolated from the tuber of Sparganium stoloniferum. The structures of both new compounds were determined on basis of spectroscopic means including HR-ESI-MS, 1D and 2D NMR experiments.

3-Methyl-4,5-dihydro-oxepine, polyoxygenated seco-cyclohexenes and cyclohexenes from Uvaria flexuosa and their anti-inflammatory activity.

The phytochemical investigation of the methanolic extract of Uvaria flexuosa (Annonaceae) leaves led to the isolation of seven compounds including, 3-methyl-4,5-dihydro-oxepine (flexuvaroxepine A), four polyoxygenated seco-cyclohexene (flexuvarin A-D) and two polyoxygenated cyclohexene (flexuvarol A-B) derivatives, together with four known flavones. The structures of the isolated compounds were elucidated using different spectroscopic techniques. A plausible biogenetic route of the new compounds was discussed. The anti-inflammatory activity of the isolated compounds was evaluated by superoxide anion generation and elastase release assays. Among the tested compounds, flexuvarol B and chrysin showed the most potent anti-inflammatory effect by inhibiting superoxide anion generation and elastase release from human neutrophils in response to fMLP with IC50 2.25-5.55µM. Moreover, 5-hydroxy-6,7-dimethoxy-flavone showed selective inhibitory activity on superoxide anion generation (IC50=1.19±0.34µM).

[Herpetolide C:one new 7H-dibenzo[c,e]oxepin-5-one from Herpetospermum caudigerum].

The chemical constituents of Herpetospermum caudigerum were investigated using chromatographic methods, including silica gel column chromatography, Sephadex LH-20 and semi-preparative HPLC. Four compounds were isolated and their structures were elucidated by spectral data and physicochemical properties, which were identified as 2,11-dimethoxy-3,9-dihydroxy-7 H-dibenzo[c,e]oxepin-5-one (1),7,8'-didehydroherpetotriol(2), herpetotrio l(3) and kaempferitrin (4). Among those, compound 1 is one new 7H-dibenzo[c,e]oxepin-5-one, named as herpetolide C.

Dibenz[b,f]oxepin and Antimycobacterial Chalcone Constituents of Empetrum nigrum.

Two new dibenz[b,f]oxepins, empetroxepins A and B (1 and 2), and seven known compounds (3-9) were isolated from an extract of the Canadian medicinal plant Empetrum nigrum that significantly inhibited the growth of Mycobacterium tuberculosis H37Ra. The structures of 1 and 2 were established through analysis of NMR and MS data. The antimycobacterial activity of the plant extract was attributed primarily to the presence of two chalcone derivatives (6 and 7) that exhibited selective antimycobacterial activity (IC50 values of 23.8 and 32.8 µM, respectively) in comparison to mammalian (HEK 293) cells (IC50 values of 109 and 249 µM, respectively).

Lichen Secondary Metabolite, Physciosporin, Inhibits Lung Cancer Cell Motility.

Lichens produce various unique chemicals that can be used for pharmaceutical purposes. To screen for novel lichen secondary metabolites showing inhibitory activity against lung cancer cell motility, we tested acetone extracts of 13 lichen samples collected in Chile. Physciosporin, isolated from Pseudocyphellaria coriacea (Hook f. & Taylor) D.J. Galloway & P. James, was identified as an effective compound and showed significant inhibitory activity in migration and invasion assays against human lung cancer cells. Physciosporin treatment reduced both protein and mRNA levels of N-cadherin with concomitant decreases in the levels of epithelial-mesenchymal transition markers such as snail and twist. Physciosporin also suppressed KITENIN (KAI1 C-terminal interacting tetraspanin)-mediated AP-1 activity in both the absence and presence of epidermal growth factor stimulation. Quantitative real-time PCR analysis showed that the expression of the metastasis suppressor gene, KAI1, was increased while that of the metastasis enhancer gene, KITENIN, was dramatically decreased by physciosporin. Particularly, the activity of 3'-untranslated region of KITENIN was decreased by physciosporin. Moreover, Cdc42 and Rac1 activities were decreased by physciosporin. These results demonstrated that the lichen secondary metabolite, physciosporin, inhibits lung cancer cell motility through novel mechanisms of action.

Varioxepine A, a 3H-oxepine-containing alkaloid with a new oxa-cage from the marine algal-derived endophytic fungus Paecilomyces variotii.

A new 3H-oxepine-containing alkaloid, varioxepine A (1), characterized by a structurally unprecedented condensed 3,6,8-trioxabicyclo[3.2.1]octane motif, was isolated from the marine algal-derived endophytic fungus Paecilomyces variotii. Due to the low proton/carbon ratio, the unambiguous assignment of the planar structure and relative configuration was precluded by NMR experiments and solved by single crystal X-ray analysis. The absolute configuration was established by DFT conformational analysis and TDDFT-ECD calculations. Compound 1 inhibited plant pathogenic fungus Fusarium graminearum.

Potent microbial and tyrosinase inhibitors from stem bark of Bauhinia rufescens (Fabaceae).

The stem bark extracts of Bauhinia rufescens Lam. (Fabaceae) yielded 6-methoxy-7-methyl-8-hydroxydibenz[b,f]oxepin, alpha-amyrin acetate, beta-sitosterol 3-O-beta-D-xylopyranoside, 4-(2'-Hydroxyphenethyl)-5-methoxy-2-methylphenol, menisdaurin and sequoyitol. Their structures were determined using spectroscopic methods and comparisons with the literature data. For the antimicrobial assay Gram-positive and Gram-negative bacterial and fungal strains were tested, while the tyrosinase inhibition assay utilized L-DOPA as a substrate for the tyrosinase enzyme. 6-Methoxy-7-methyl-8-hydroxydibenz[b,f]oxepin, a-amyrin acetate, beta-sitosterol 3-O-D-xylopyranoside, menisdaurin and sequoyitol showed weak to moderate activities with minimum inhibition concentration (MIC) values in the range of 112.5-900 microg/mL against all bacterial strains, while the MIC values for the fungal strains were in the range of 28.1-450 microg/mL. In the tyrosinase inhibition assay, a-amyrin acetate was found to be moderately active against tyrosinase with an inhibition of 62% at 0.1 mg/mL. This activity was lower than that of the positive control, kojic acid (85%).

Depsidones, aromatase inhibitors and radical scavenging agents from the marine-derived fungus Aspergillus unguis CRI282-03.

Three new depsidones ( 1, 3, and 4), a new diaryl ether ( 5), and a new natural pyrone ( 9) (synthetically known), together with three known depsidones, nidulin ( 6), nornidulin ( 7), and 2-chlorounguinol ( 8), were isolated from the marine-derived fungus ASPERGILLUS UNGUIS CRI282-03. Aspergillusidone C ( 4) showed the most potent aromatase inhibitory activity with the IC (50) value of 0.74 µM, while depsidones 1, 3, 6- 8 inhibited aromatase with IC (50) values of 1.2-11.2 µM. It was found that the structural feature of depsidones, not their corresponding diaryl ether derivatives (e.g. 5), was important for aromatase inhibitory activity. Aspergillusidones A ( 1) and B ( 3) showed radical scavenging activity in the XXO assay with IC (50) values of 16.0 and < 15.6 µM, respectively. Compounds 1 and 3- 7 were mostly inactive or showed only weak cytotoxic activity against HuCCA-1, HepG2, A549, and MOLT-3 cancer cell lines.

New stress metabolite from Bulbophyllum kwangtungense.

A new dibenz[b,f]oxepin (1) was found to be produced as a stress metabolite from the leaves and stems of Bulbophyllum kwangtungense Schlecht, in response to abiotic stress elicitation by CuCl2. The structure of 1 was established by spectroscopic and spectrometric means.

Protuboxepins A and B and protubonines A and B from the marine-derived fungus Aspergillus sp. SF-5044.

Two new oxepin-containing (1 and 2) and two diketopiperazine-type alkaloids (3 and 4) have been isolated from an EtOAc extract of the marine-derived fungus Aspergillus sp. SF-5044. The structures of these metabolites were determined through analysis of NMR and MS data, along with Marfey's method. Compound 1 showed weak growth inhibitory activity against a small panel of cell lines.

Psammaplysin H, a new antimalarial bromotyrosine alkaloid from a marine sponge of the genus Pseudoceratina.

Mass-directed isolation of the CH(2)Cl(2)/CH(3)OH extract from a marine sponge of the genus Pseudoceratina resulted in the purification of a new antimalarial bromotyrosine alkaloid, psammaplysin H (1), along with the previously isolated analogs psammaplysins G (2) and F (3). The structure of 1 was elucidated following 1D and 2D NMR, and MS data analysis. All compounds were tested in vitro against the 3D7 line of Plasmodium falciparum and mammalian cell lines (HEK293 and HepG2), with 1 having the most potent (IC(50) 0.41µM) and selective (>97-fold) antimalarial activity.

Phenolic compounds with cell protective activity from the fruits of Livistona chinensis.

Two new depsidones, livistones A (1) and B (2), and a new benzofurane, livistone C (3), together with the 11 known compounds including three stilbenes (4-6), four steroids, three flavan-3-ols, and an alkaloid were isolated from the fruits of Livistona chinensis. The structures of the new compounds were determined by spectroscopic methods. Compounds 1, 4-6 exhibited remarkable cell protective activities against H(2)O(2)-induced SH-SY5Y cell damage.

An oxepinoflavone from Artocarpus elasticus with cytotoxic activity against P-388 cells.

A new oxepinoflavone, artoindonesianin E1 (1), was isolated from the wood of Artocarpus elasticus, along with four known prenylated flavones: artocarpin (2), cycloartocarpin (3), cudraflavones A (4) and C (5). The structure of the new compound was identified by spectroscopic methods. Upon cytotoxic evaluation against murine leukemia P-388 cells, the new compound showed IC(50) 5.0 microg/mL.